Known methods for blood pressure measurements typically involve application of pressure from an external pressure device, e.g. occlusive cuff or other pressure generating devices. These interfering methods generating an external pressure may have a significant impact on the person and the blood pressure.
Blood pressure can be measured in a number of ways, such as invasive pressure sensor, oscillometric, auscultatory and tonometric. These methods will inevitably affect the state of the patient, e.g. require surgery or use of an occlusive cuff applying an external pressure to the artery. It has been reported that a considerable number of measurements performed at the office of a medical doctor or at a hospital are affected by the situation and may be quite erroneous compared to what would have been measured if the patient had not been affected by the medical environment. The golden standard for blood pressure measurement is an invasive pressure measurement implying considerable risk for the patient. The variations of the blood pressure in relation to the activity of the patient may provide very important information in relation to diagnosis.
Vascular compliance can be measured in a number of ways. An indirect method is based on evaluating the temporal shape of the blood pressure. Such method involves several assumptions, which may not be fulfilled. Ultrasound may be applied for direct wall displacement measurement. The ultrasound method relies on a good knowledge of the ultrasound velocity and at the same time characteristic acoustic propagation perturbations.
These methods are not suitable for ambulatory measurements. Thus, there is a need for a non-interfering scheme for measuring blood pressure and/or vascular compliance which scheme can be applied for ambulatory measurements and/or outside hospitals and other medical facilities.
Continuous monitoring of blood pressure has been reported to be an important parameter both in diagnostics and prognostics.
Non-invasive and non-interference methods for measuring vascular compliance and blood pressure generally suffer from the problem that too many assumptions about both dimensions, material properties, and curve shape of the temporal evolution of signals are needed in order to obtain useful measurements.
Existing methods do not provide non-interfering recording of blood pressure neither during sleep nor during physical activity.